PCT international patent application publication WO91/12413 (Lotus) published 22 Aug. 1991 discloses valve lift control devices of various forms which provide variable valve lift. In one embodiment, a lifter has a cylindrical high lift outer cam follower that engages a pair of spaced cams for high lift valve actuation and a low lift inner cam follower that engages a central low lift cam directly or through an intermediate follower member for low lift valve actuation.
The inner follower is reciprocable in a bore of the outer follower and directly actuates the valve through a hydraulic lash adjuster. The outer follower is reciprocable in a bore of an associated engine component and is selectively connectable to the inner follower by locking means. These, when engaged, cause the inner follower to move with the outer follower, thereby actuating the valve in a high lift motion determined by the profiles of the high lift cams.